Macrocyclic polyethers, generally known as "crown ethers", were first described by Charles Pedersen. See generally C. J. Pederson, J. Am. Chem. Soc. 89:26, 7017 (Dec. 20, 1967). Numerous variations have been made to produce a group of compounds known as crown ligands or macrocyclic ligands.
The attachment of redox centers to crown ethers was first described by Dr. Fritz Vogtle. Such compounds are of interest because the coordinating ability (binding strength and/or selectivity) can be altered by physical or chemical means. Redox active macrocyclic ligands that have been produced to date include ferrocene derivatives, tetrathiafulvalene derivatives, and quinone derivatives. See generally P. Beer, Chem. Soc. Rev. 18, 409 (1989); P. Beer., Chem. Soc. Rev. 39, 79 (1992); T. Jorgensen et al., Chem. Soc. Rev. 23, 41 (1994); R. Dieing et al., J. Chem. Soc., Perkin Trans., 1587 (1996); Z. Chen and L. Echegoyen, in Crown Compounds Toward Future Applications, p. 27 (S. Cooper Ed. 1992).